I love the textures and the volumes of the clothes in this!
I'm surprised nobody mentioned the face, though. Even for a stylised piece I had difficulties recognising Freud - the proportions don't feel right. You put emphasis on his forehead, but I associate Freud more with his beard, so I'd suggest exaggerating that instead. You could also consider putting in his iconic frown, and I think with these two traits you can pull off a convincing Freud.
Here's an edit:
Hope it helps :)